uboot-imx

arm: ti: boot: Extract PARTS_DEFAULT to boot.h

Eliminate code duplication: the same PARTS_DEFAULT was defined in
am57xx_evm.h and in dra7xx_evm.h. Extract it to environment/boot.h and
use in all OMAP5-based boards.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>